Changes in activity and subcellular localization of alpha-like DNA polymerase during cell cycle of Physarum polycephalum.

Regulation of DNA replication was given attention by examining the subcellular localization of alpha-like DNA polymerase in Physarum polycephalum. The activity per plasmodium increased by 2-fold in the cytoplasm during the G2-phase, and decreased with a concomitant increase in nuclei prior to DNA replication. This would suggest that the enzyme translocates from the cytoplasm to the nucleus, co-ordinately with DNA replication. In nuclei, the nuclear matrix-bound activity increased during the S-phase, but changes did not always parallel the rate of DNA replication. On the other hand, the activity measured without exogenous templates did change with the rate, although the activity was low. It is, therefore, suggested that part of the enzyme binding with the matrix participates in DNA replication.